1. Field of the Invention
The present invention relates to an image processing device, an imaging device, an image processing method, and a non-transitory computer readable recording medium recorded with an image processing program.
2. Description of the Related Art
Digital cameras which have a so-called manual focus mode that enables the user to manually adjust focus, in addition to an automatic focus mode using a phase difference detection method or a contrast detection method, is widely known.
As a digital camera having the manual focus mode, a digital camera is known which is provided with a reflex mirror such that the user can adjust focus while checking an object and uses a split microprism screen on which a phase difference is visually displayed. In addition, a digital camera using a method which visually checks contrast is known.
However, in a digital camera without a reflex mirror which has recently come into widespread use, since a reflex mirror is not provided, there is no way to check an object image while displaying a phase difference and there is no choice but to use the contrast detection method. However, in this case, it is difficult to display an image with a contrast that is equal to or greater than the resolution of a display device, such as a liquid crystal display (LCD). As a result, there is no choice but to use a method which partially enlarges an image or the like and displays the image.
In recent years, a split image has been displayed in a live view image (also referred to as a through image) in order to make it easy for the user (for example, the photographer) to focus the camera on the object in the manual focus mode. The split image indicates, for example, a divided image of which the display region is divided into a plurality of regions (for example, each of the images which are divided in the up-down direction) and which deviates in a direction in which parallax occurs (for example, the left-right direction) depending on the amount of defocus. When an image is in focus, the deviation of the split image in the direction in which parallax occurs is removed. The user operates a manual focus ring (hereinafter, referred to as a “focus ring”) to focus the camera on the object such that the deviation of the split image (for example, each of the images which are divided in the up-down direction) is removed.
Here, the principle of the split image will be described with reference to the imaging device disclosed in JP2009-147665A. The imaging device disclosed in JP2009-147665A generates a so-called right eye image and a so-called left eye image from an object image which passes through a pair of regions of an imaging lens, is pupil-divided, and is formed. Then, the imaging device generates a split image using the right eye image and the left eye image, and generates a normal image from an object image which passes through the imaging lens, without being pupil-divided, and is formed. Then, the imaging device displays the normal image on a display unit and displays the split image in the normal image.
However, since the center of a light flux which passes through the pair of regions of the imaging lens deviates from the optical axis of the lens, linear shading characteristics appear in the right eye image and the left eye image in each direction along a pupil division direction.
WO2012/039346A discloses a technique for correcting the shading characteristics. The imaging device disclosed in WO2012/039346A compares a pixel value included in a normal image with pixel values included in a right eye image and a left eye image, creates a correction table, and corrects the shading characteristics using the created correction table.